2) Surely, you do not mean using 4 tubes at the same exact time? :) But yes, you can use both of these tubes in your LD MKIII. There are jumpers on the circuit board that allow you to change the configuration of your amp to play either EF95 or EF92 tubes. So it is simply a matter of setting the jumpers correctly in order to use these tube types.

I mean, they are different types EF95 and EF92 and the manual just say how to change the jumpers in order to use one of them. I am not sure if I can use BOTH of them

I am just curious about what you mean with "lesser hands" in terms of sound. I seem to remember a mention that your Pinnacle mystery tubes looked cheaply made, yet sounded excellent.

Some people have mentioned that the LD MKIII itself seems to be lacking 100% craftsmanship, but as far as I am concerned it is built like a tank, and able to take almost anything you throw at it. Can only remember one or two instances when somebody had a problem necessitating repair, and then it seems it was done for free, even long after the warranty period was over.

In summary, the sound is what matters to me, and obviously the excellent price point.

On another note: Did you have a chance to compare the NEC 6AV6 to Pinnacle?

Did Yang Sword communicate with you?

No no, by "lesser hands", I'm just referring to what I've read on this EI company. It's just the typical example where technology is transferred from one factory to an other, and that new factory just doesn't make stuff that's quite as good as the old factory. Think of having the knowledge but not the experience. People buy tubes from companies like EI or Matsush*ta because they are looking for the Mullard/Philips sound but would rather pay 20% of the price for 90% of the quality. If anything, my EI ECC88 look very solidly made!

I only got to spend very little time with the NEC 6AV6. While I thought that they were at least decent, they did kind of show the typical "single triode in our LD amps" syndrome, and weren't exactly the most musical tubes. Detailed and balanced though, for sure.

I have not heard from the folks at LD since I mentioned anything technical in our exchanges. They clearly don't like to divulge their secrets...

Since half the know world wants 12AX7, the price for those tends to ramp up quickly.

Indeed. Personally, I think that the beauty of this thread is the love for the oddball types. Why use a 12AX7/ECC83 when you can use two 6AV6/EBC91 tubes? In either case, you have two triodes that are all equivalent to each other.

..., we have seen Mullard/Blackburn made Siemens EH90s with "Made in Germany" written on them, and a number of other misleadingly labeled tubes, so I don't necessarily trust what is written on the tube....

I quite agree, in general.

In fact, I wonder whether your GE "Made in Great Britain" 6HM5 tubes without Mullard codes are examples of this. GE certainly did not make them in the UK.

In fact, I wonder whether your GE "Made in Great Britain" 6HM5 tubes without Mullard codes are examples of this. GE certainly did not make them in the UK.

I have been wondering about this too.... GE claims to have had a presence in the UK since the 1930s, but I have not seen any evidence that they had factories there. And further, these tubes do not have the tube number and dots sandblasted into the glass as is typical for GE-manufactured tubes. So if they were actually made in the UK for GE, but not by a Philips subsidiary, then perhaps it was another UK-based manufacturer?

Some manufacturers with Philips tooling were less devoted to the codes. Ei, BEL, Matsush¡ta, at least. But the internal construction is the key.

And that's the rub... Their internal construction is different than Philips 6HM5 tubes such as Ei, Siemens and GE/Blackburn 6HM5. I have not seen any other tubes like these. So in the end, we have these GE 6HM5 tubes, purportedly made somewhere in Great Britain, by an unknown manufacturer....

Just a small observation on the sound differences between 6DT6 tubes...

RCA 6DT6A haven't changed much and remain warm, detailed and expansive. Good bass and treble extension (I'm well over 100 hrs of use) (Square getter and black plates)

Sylvania 6DT6A my initial review was done around 10 hrs because these seem to have settled BUT now nearing 100 hrs I've noticed they sound a lot less like the RCA's then I reported (I have another set that have not had much use to compare (15 hrs maybe) These are not as warm as the RCA's slightly better bass impact, and better detail retrieval (a by product of less warmth) (Just noticed these have halo getters... grey plates)